1. Field of the Invention
The invention pertains to a cooking utensil, for example a pot or a frypan with a container liner of stainless steel with a comparatively low wall thickness and a comparatively thick bottom plate of aluminum or a material of similarly good heat-conducting properties on the outside bottom of the container liner which plate is attached to a bottom disc on the outside of the bottom plate that is at least partially composed of magnetizable material.
2. Description of Related Art
As opposed to for example enamel-on-steel cooking pots, stainless steel utensils for gas or electric ranges are appreciated for durability, good cleaning properties and attractive appearance. However, since stainless steel has a comparatively low heat-conductivity the container of the cooking utensil with its comparatively thin wall thickness is commonly provided with a comparatively thick bottom plate of aluminum or a material of similarly good heat-conducting properties. As a result of its good heat-conductivity, even if only locally heated, the bottom plate ensures an even simmering process across the entire inner bottom surface. A cooking utensil according to DE-OS 22 58 795 has a bottom plate of aluminum or a material of similarly good heat-conducting properties which employs a protective layer of stainless steel on the outside of the bottom plate with features identical to those of the container liner.
Cooking utensils of the kind commonly described consist of austenitic steel, and therefore they are not suited for the use on so-called induction stoves, because steels of austenitic structure are not or are only minimally magnetizable for the heating of the cooking utensil including its food items with the help of magnetic alternating fields.
In order not to be limited to gas or electric range use, and to include applications for induction stoves as well, a cooking utensil of stainless steel has been disclosed in an earlier not pre-published patent application U.S. Pat. No. 36 34 841.4 which consists of a bottom plate comprised of an intermediate layer of ferritic steel which is encapsulated by outer layers of austenitic steel. This solution is relatively complicated and costly due to a bottom disc of three layers.
In an earlier not pre-published patent application U.S. Pat. No. 36 39 013.5 another type of cooking utensil of the kind described heretofore is disclosed that is suited for use on gas and electric ranges as well as for induction stoves. Therein a bottom disc of aluminum or a material of similarly good heat-conducting properties is connected on its outside surface to a bottom disc of austenitic steel with magnetizable material of low thickness applied to the outside surface of the latter.
It is an object of the present invention to introduce a cooking utensil of the kind heretofore described, which is of simpler construction and provides a more effective application to an induction stove while reliably retaining a good and even transmission of heat and an even contact surface when heated on an electric range.
According to the invention this object is accomplished with a bottom disc which essentially consists of nickel or a nickel alloy or at least an intermediate layer of a nickel alloy. Surprisingly it has turned out that at such construction of a bottom layer due to the bimetal effect and/or the mix-expansion when heated results in a compensation such that the contact surface of the bottom remains reliably flat. Nickel or nickel alloys furthermore are of a very high magnetic permeability so that a relatively low layer thickness is possible to provide a more effective use on induction type stoves. Nickel furthermore can easily be formed and is particularly well plated, which results in an inexpensive production.
Furthermore, bottom discs according to the invention exhibit good resistance to corrosion.